Due to its excellent mechanical properties (e.g., tear strength, tensile strength, flex life, and abrasion resistance), polymeric compositions based on copolyetherester elastomers have been used in forming components for motorized vehicles and electrical/electronic devices. However, often times, electric arc may be formed and high temperature may be reached within the under-hood areas of vehicles and inside electrical/electronic devices. Thus, while maintaining other mechanical properties, it is desirable that such copolyetherester based compositions also have low flammability and high thermal stability.
Various flame retardant systems have been developed and used in polymeric material, e.g., polyesters, to improve the flame-retardancy thereof. However, due to toxicity concerns, halogen-free flame retardants are gaining more and more attention. Among the various halogen-free flame retardants, phosphorus compounds (such as salts of phosphinic or diphosphinic acids) are used the most due to the stability and flame retardant effectiveness thereof. Prior art has also demonstrated that various types of synergistic compounds can be used as synergists in combination with the phosphorus compounds to further maximize the flame retardant effectiveness thereof. For example, U.S. Pat. No. 6,547,992 discloses the use of synthetic inorganic compounds such as oxygen compounds of silicon, magnesium compounds, metal carbonates of metals of the second main group of the periodic table, red phosphorus, zinc compounds, aluminum compounds, or combinations thereof as flame retardant synergists; U.S. Pat. No. 6,716,899 discloses the use of organic phosphorus-containing compounds as flame retardant synergists; U.S. Pat. No. 6,365,071 discloses the use of nitrogen-containing compounds (e.g., melamine cyanurate, melamine phosphate, melamine pyrophosphate, or melamine diborate) as flame retardant synergists; and U.S. Pat. No. 6,255,371 discloses the use of reaction products of phosphoric acids with melamine or condensed product of melamine (e.g., melamine polyphosphate (MPP)) as flame retardant synergists.
Particularly, European Patent Publication No. EP1883081 and PCT Patent Publication Nos. WO2009/047353 and WO2010/094560 each discloses flame retardant elastomeric compositions useful in forming the insulating layers and/or jackets of wires and cables. In those disclosures, combinations of (i) a metal salt of a phosphinic acid and/or a diphosphinic acid, (ii) a nitrogen containing compound (e.g., melamine polyphosphate), and (iii) an inorganic compound (e.g., zinc borate) are taught as preferred flame retardant packages. Also, Korean Patent No. KR 2010038701 discloses a flame retardant package useful in copolyetherester, which comprises an organic phosphinate metal salt, a melamine cyanurate, and an aromatic phosphate. However, as demonstrated in the examples below, the present Applicant discovered that when such prior art flame retardant packages are used in copolyetherester compositions, the flame retardants tend to migrate to the surface over time and cause blooming. Thus, there is still a need to develop a flame-retardant copolyetherester composition that is blooming free.